Lecture 4: Respiratory Flashcards
What is the difference between respiration and ventilation?
Ventilation is the movement of air in and out of the lungs.
Respiration is the exchange of gases.
What is the ventilation perfusion ratio? Where is it high and low?
It is the ratio of alveolar ventilation relative to pulmonary blood flow.
Starting from the top of the lungs, it is high, at 2.1.
In the middle, it goes to 1.
At the bottom of the lungs, it goes to 0.3.
When is the work of breathing? Inspiration or expiration?
Inspiration.
What are the two mechanisms that expand and contract our lungs?
Movement of the ribcage using the intercostal muscles. (elevation and depression of the ribs to increase and decrease anterposterior diameter of the chest cavity)
Contraction and relaxation of the diaphragm to adjust the chest cavity volume. (- to lengthen or shorten the chest cavity)
What is the key limiting factor for all people in terms of exercise?
It is our cardiometabolic limits, not our lungs.
During NORMAL expiration, what occurs?
Relaxation of the diaphragm.
Elastic recoil of both the lungs and chest wall.
During HEAVY expiration, what occurs?
Relaxation of the diaphragm.
Use of abdominal & intercostal muscles.
During HEAVY inspiration, what occurs?
Contraction of the diaphragm.
Use of external intercostals, sternocleidomastoid, anterior serrati, and scaleni muscles.
What king of pressure does inspiration generate? What pressure are our lungs at relative to the environment?
Negative pressure. Air is sucked into our lungs because the pressure INSIDE is LOWER than outside.
Inside pressure is 754mm Hg usually.
Why do people with lung disease seem more tired?
Breathing is energy intensive.
describe a lung
elastic structure that collapses like a balloon and expels all its air through the trachea whenever there is no force to keep it inflated.
Where is the lung attached to the chest wall?
At the hilum from the mediastinum.
Which parietal surface is found directly on the lungs?
Visceral pleural surface lining.
Which pleural surface is found on the thoracic cavity?
Parietal pleural surface lining.
What maintains the suction between the two pleural surfaces?
pleural fluid, which is continually suctioned into the lymphatic channels. It helps create a seal, similar to a drop of water between two glass surfaces.
What does pleural pressure usually measure at?
-5 to -7.5 cm H2O.
when does alveolar pressure = 0
when the epiglottis is open (no airflow)
During inspiration, what occurs to alveolar pressure?
It falls by approximately 1cm H2O.
What does the change in alveolar pressure during inspiration cause?
Negative pressure, usually sucking in 500 mL of air into the lungs, AKA our tidal volume.
During expiration, what occurs to alveolar pressure?
It increases by approximately 1cm H2O back to its original pressure.
What is trans-pulmonary pressure? How do I measure it?
Difference between alveolar pressure and pleural pressure.
What is recoil pressure? what is it equal to?
It is a measure of the elastic forces in our lungs that collapse our lungs at the end of inspiration. equal to trans-pulmonary pressure.
What two fibers make up the elasticity of our lung?
Elastin and Collagen.
where are collagen and elastin and what state are they in
they are interwoven among the lung parenchyma (thin wall of alveoli). and they are in a kinked, elastically contracted state.
What happens to our lung fibers as our lung expands?
They start stretching and unkinking, exerting the elastic force that makes expiration easy relative to inspiration.
What does poor lung compliance mean?
It means our lungs are stiff, so it requires more effort INSPIRING to generate the elastic force that makes expiration easy.
In other words, people with poor lung compliance have difficulty INSPIRING.
What two mechanisms determine our lung’s elastic force?
The lung fibers themselves (elastin and collagen)
Surface tension within the alveoli.
Which mechanism generates most of the elastic recoil in expiration?
Surface tension = 2/3.
The elastic force due to tissues (elastin and collagen) are responsible for only 1/3.
Why do we care that alveolar fluid interacts with air instead of more water?
The surface tension is generated when air meets water. The water has a stronger attraction for other water molecules if it meets air.
describe the difference between a saline filled lung and a air filled lung
saline filled will have :
- no air-water interference
- no surface tension
- only elastic forces at work
- very little transplural pressure required to expand
-3x force needed to exapnd the air filled lung
Clinical Question: What is a pneumothorax and the two kinds?
Pneumothorax: Collection of air in the chest OUTSIDE of the lung, causing lung collapse.
Primary pneumothorax: Occurs without apparent cause in the absence of lung disease.
Secondary pneumothorax: Occurs in the presence of existing lung pathology.
Special: A tension pneumothorax is created via one-way valves made from an area of damaged tissue, so the lungs slowly get squeezed. Leads to decreasing spo2 and low BP.
What makes surfactant in the lungs? What is surfactant?
Type II alveolar epithelial cells.
Surfactant is an agent that reduces the surface tension of water.
Note: laundry detergent is also a type of surfactant.
When do babies start making surfactant?
6-7 months of gestation, or 24-28 week which is when their type II alveolar epithelial cells develop.
Note: A baby’s lungs are usually fully developed around 32-36 weeks.
What is the key differences between a restrictive lung disease and an obstructive lung disease?
Restrictive lung diseases show reductions in all lung capacity measurements, such as VC, FRC, TLC, and FVC.
Obstructive lung diseases show a marked decrease in the ability to expire.
Name some restrictive lung diseases.
Idiopathic pulmonary fibrosis (IPF)
Non-specific interstitial pneumonia (NSIP)
Cryptogenic organizing pneumonia (COP)
Sarcoidosis
Acute interstitial pneumonia (AIP)
Name some common obstructive lung diseases.
Emphysema
Asthma
Chronic bronchitis
Note: COPD refers to most of the obstructive diseases. Also, these are all NON-reversable.
What disease do I commonly see barrel chest in?
Emphysema
What is the average tidal volume? (In terms of what we learned class-wise)
500 mL
What do capacity measurements include that reserve volumes do not for lung measurements?
Any reserve volume measurement does NOT include tidal volume.
Any capacity is a combination of 2 or more things.
Example: Functional vital capacity is the addition of Inspiratory reserve volume (IRV) + Tidal Volume (TV) + Expiratory reserve volume (ERV)
What is minute ventilation? The normal average?
The volume of air we breathe in one minute.
It is normally 6L, which is 12 breaths/min X 500 mL/breath. AKA breathing rate x tidal volume.
How much dead space is in our tidal volume?
150mL
What two things make up dead space?
Anatomic dead space and physiologic dead space.
Anatomic dead space = trachea and the parts of the airway that are not alveoli. (very tippy top of lungs, no alveoli)
Physiologic dead space = the parts of the alveoli that have bad perfusion. (well ventilated but poorly perfused)
What is the main disadvantage with shallow breathing relative to minute ventilation?
Overventilation of the dead space.
Shallow breathing with high respiratory rate commonly does not exceed the dead space, since our tidal volume is decreased per breath.
What are the main disadvantages with deep breathing in regards to minute ventilation?
Tiring of the intercostal muscles.
Inadequate exhalation of CO2.
How do we measure alveolar minute ventilation?
It is the difference between our total minute ventilation and our dead space minute ventilation.
Clinical: How do we check if someone has an obstructive lung disease? What do we measure, and at what point is it clinically significant?
We measure FEV1/FVC, which is the forced expiratory volume in 1 second divided by the functional vital capacity. In other words, it is how much I can exhale in a single second relative to my total lung capacity - the dead space in my lungs.
Example: My Predicted FEV1 is 4L. My actual FEV1 is 3L. I would say that I am at 75% of predicted.
Ideally, we want 80%, but if you go down to 60%, then we consider that concerning.
Note: Asthma is one of the few reversible lung diseases, whereas chronic ones are not.
What kind of rings does my trachea have? Why?
Cartilage, to help prevent collapse.
What is a key difference between my bronchi and trachea?
My bronchi have LESS cartilage, therefore they can expand and contract more.
What keeps my bronchioles expanded?
Rigidity of their walls + transplumonary pressure. This is the same pressure that also keeps alveoli expanded.
Why are bronchi and bronchioles the site of narrowing in obstructive lung diseases?
They are mainly made of smooth muscle, which contracts. The obstructive lung diseases can cause excessive contraction.
When does the conducting zone end?
After the 16th division within the bronchioles.
When does the respiratory zone begin?
At the 17th division within the bronchioles, where alveoli start appearing on the bronchioles.
Clinical: What is significant about the respiratory zone in regards to particulates?
Air moves very slowly in this zone, so particulates tend to just settle here and stay. This is the reason things like coal dust or asbestos can cause gradual lung symptoms.
